1. Field of the Invention
The present invention relates to a waterproof box such as an electrical junction box which is used for wiring arrangement in a motor vehicle or the like, and more particularly to a structure for mounting a cover to a container body of the waterproof box which can ensure reliable waterproofing performance.
2. Description of the Related Art
There have been heretofore employed, in motor vehicles, waterproof boxes, for example, electrical junction boxes such as a junction box, fuse box, relay box, etc. in order to contain various parts required for connecting and treating wire harnesses in the vehicle, and electrical components such as fuses, relays, electronic control unit, etc.
Various types of the electrical junction boxes have been employed according to types of the vehicles. For example, various types of electrical components are contained in a box-like container made of synthetic resin or the like, which is composed of a container body and a cover.
Because the electrical junction box is generally arranged at side areas in a lower part of a vehicle body, there has been such an anxiety that the components such as circuits may cause a short circuit or a leaked current may flow, when water has intruded into an interior while driving in rain or during car wash. Therefore, it is necessary to render the electrical junction box waterproof. In case of washing a large car especially, high pressure water jetted with force is liable to intrude into the electrical junction box.
Specifically, the water which has collided against a side wall of the container body will sometimes flow along the side wall, enter between the side wall and the cover, and intrude into the container body. For this reason, it has been proposed that the side wall of the container body is formed to have a double-wall structure consisting of an outer wall and an inner wall. According to this structure, even though the water which has collided against the side wall has flowed along the side wall, and entered between the side wall and the cover, the water will intrude between the double walls, that is, between the outer wall and the inner wall. This water intruded between the double walls will lose force, and intrusion of the water into the container body can be restrained.
As another countermeasure, it has been proposed that a packing is provided between the cover and the container body, and waterproofing performance is ensured by compressing this packing to seal the cover with respect to the container body. However, in case where the cover is locked to the container body by resin-to-resin lock, compression rate of the packing may be low. For this reason, it has been further proposed that the lock between the cover and the container body is reinforced by employing a locking piece made of metal, in other words, the compression rate of the packing may be increased by engaging one end of this locking piece with the container body while the other end is engaged with the cover, thus enabling the cover to be rigidly pressed to the container body.
However, in the former case, on occasion of forming the side wall of the container body in the double-wall structure consisting of the outer wall and the inner wall, a gap between the outer wall and the inner wall has been made as small as possible in order to secure as large as capacity inside the container body. On that account, the gap between the outer wall and the inner wall may become smaller due to tolerances between the walls or inclination, which leads to bad assembling performance. As shown in FIG. 10, when a cover 71 is mounted to a container body 70, it sometimes happens that a lower end of an inner wall portion 72 of the cover 71 is not accurately positioned between an outer wall 73 and an inner wall 74 of the container body 70, but, for example, abutted against the outer wall 73. As the results, the container body 70 and the cover 71 are not favorably engaged with each other, resulting in a so-called half-engaged state. If the cover 71 should be pressed onto the container body 70 in this state, waterproofing performance may be deteriorated.
In the latter case, as shown in FIGS. 11 and 12, when a cover 81 is mounted to a container body 80, it sometimes happens that alignment between the container body 80 and the cover 81 cannot be accurately made due to variation in respective tolerances or inclination, in short, the cover 81 is not favorably mounted to the container body 80. Even though the container body 80 and the cover 81 should be tightened in this state by means of a locking hook 82, they cannot be rigidly pressed to each other, and the compression rate of the packing will not be increased. In such case, the waterproofing performance may be deteriorated.
The present invention has been made in view of the above described circumstances, and an object of the invention is to provide a cover mounting structure of a waterproof box by which reliable waterproofing performance can be ensured.